Abstract: Based on the hypothesis that the yarns′cross-section shape is race-track and the analysis of microstructure,a mathematical model was proposed for the fiber volume fraction of multidirectional filament wound glass-fiber/epoxy tubes.According to the model,the fiber volume fraction is related to tow bandwidth,tow thickness,total number of winding cycles,helical winding angle,the inner radius of the product and the yarn gap,but not to the length of the cylinder.Furthermore,four specimens were wound with the same materials but different process parameters,and the results indicated that the fiber volume fraction from the model are in basic agreement with that of the experiment,which means though some variations exist,the model is practical.Finally,the main factors leading to the deviations of the theoretical value were analyzed,they were probably attributed to the ideal assumptions,influence of the porosity and so on.